Communication system



Sept 15, 1953 A. w. BoRsuM ET AL 2,652,556

COMMUNICATION SYSTEM original Filed Nov. 2e, 1945 8 Sheets-Sheet 1 NVENTORS ATTORNEY Sept. l5, 1953 A. w. BoRsuM E'rAL COMMUNICATION SYSTEM Original Filed NOV. 26, 1945 Am www L.' 0 www@ w 8 Sheets-Sheet 2 INV ENTORS ATTORNEY Sept 15, 1953 A. w. BoRsUM ET AL 2,652,556

coMMUNIcATroNsYsTEM Original Filed Nov. 26, 1945 l 8 Sheets-Sheet 5 souRcE oF E" MIXER FREQUENCY F J' m E f.' BUFFER N REsoNANT N PHASE STAGE FILTER SHIFTER SUB'HARMONIO GENERATOR JBn INVENTORS ATTORNEY pt. l5, i953 A. w. BoRsuM ITAL 2,652,556

COMMUNICATION SYSTEM Original Filed Nov. 26, 1945 8 Sheets-Sheet 4 INVENTQRS l ATTORNEY Sept 15, 1953 A. w. BoRsUM ET AL 2,652,556

COMMUNICATION SYSTEM Original Filed Nov. 2S, 1945 8 Sheets-Sheet 5 INVENTORS @www w. @www mwen, w.

ATTORNEY Sept.- l5, 1953 A. W. BoRsuM ET AL COMMUNICATION SYSTEM 8 Sheets-Sheet 6 Original Filed Nov. 26, 1945 moved-o2- INVENTOR ATTORNEY .Sept 15, 1953 A. w. BoRsUM ET AL 2,652,556

COMMUNICATION SYSTEM Original Filed Nov. 26, 1945 8 Sheets-Sheet 7 PUSH-PULL AMPLIFIE R INVENTORS DGLPM W.' @ORSUE WELWELM W. BRQGEWMY ATTORNEY Sept. i5, 1953 A. W. BORSUM ET AL 2,652,556

COMMUNICATION SYSTEM Original Filed Nov. 26, 1945 8 Sheets-Sheet 8 O O SPEED 60D E INVENTORS @im 'V @einem ATTORNEY Patented Sept. l5, 1953 NETE COMMUNICATION SYSTEM Adolph William Box-sum, United States Navy, and Wilhelm W. Brockway, West Los Angeles, Calif.

Original application November 26, 1945, Serial No. 630,957,- now Patent No. 2,582,957, dated January 22, 1952. Divided and this application February 21, 1950, Serial No. 145,514

4 Claims.

(Granted under Title 35, U. S. Code (1952),

sec. 266) Our invention relates to systems for transmis- Sion of signals convertible for example into messages, indication of course, range, or the like. The present application is a division of Ser. No. 630,957, filed November 26, 1945, now Patent No. 2,582,957, issued January 22, 1952.

In accordance with our invention, the signal transmitted is in the form of a complex wave comprising a reference frequency and one or more other components occurring at rates having fixed numerical relation to said frequency and whose timing within the reference cycle is varied in accordance with information to be conveyed. At the receiving station, the complex Wave is separated into its components which are impressed upon a phase meter, or equivalent, for translation of the received wave into the original information.

More particularly, in accordance with our invention, the complex Wave comprises a reference frequency and one or more other frequencies bearing a harmonic or sub-harmonic relation with respect thereto.

Our invention resides in the method and systems hereinafter described and claimed.

For an understanding of our invention and illustration of various forms thereof, reference is made to the accompanying drawings in which:

Figure 1 is a block diagram of a communication system.

Figures 2 and 3 are curves referred to in explanation of the system shown in Figure 1.

Figures 4 and 5 illustrate phase-shifting networks.

Figure 6 is a block diagram of a modification of the transmitter of Figure 1.

Figure 7 discloses curves referred to in explanation of Figure 6.

Figure 8 is a schematic diagram showing components of the wave shifter of Figure 1 or Figure 6.

Figure 9 is a block diagram of a modification of the receiver of Figure 1.

Figure 10 is a wiring diagram of components of Figure 9.

Figure 11 discloses an indicator usable in the receivers of Figures 1 and 9.

Figure 12 illustrates a modification of Figure 8.

Figure 13 discloses a control board for the phase-shifter shown in Figure 12.

Referring to Figure 1 for explanation of basic principles of our invention, the outputs of the sources l and 2 of different frequencies having harmonic or sub-harmonic relation to each other and a fixed time relation are impressed on the mixer stage 3 to produce a complex Wave having both frequencies as components. One of the frequencies, for example that of source 2, is used as a reference and between the other source and the mixer 3 is interposed phase-shifter 4 having an adjustable member positioned in accordance with the particular information to be transmitted.

Assuming for purpose of explanation that the frequency F of source 2 is four times that of source l, and that for zero setting of phaseshifter t the time relation of the two waves is as shown in Figures 2 and 3, the output wave of the mixer is of the shape generally shown by the dotted line curve of Figure 3. For this numerical relation of the two frequencies, as the phase-shifter t is adjusted to effect from Zero to ninety degree shift of phase of frequency F/N the shape of the output wave of the mixer assumes different forms each uniquely corresponding with an adjustment of the phase shifter.

As shown in Figure 2 each successive five degree change in adjustment of the phase-shifter may correspond with a different letter or number or each one degree change may correspond with a four degree change in azimuth. Obviously, if the ratio of the frequencies were two instead of four, the phase shifter i should be capable of alicrding phase-shift of frequency F/N within the range of 0 to 180 to afford the relation shown by Figure 2. From these two examples, the required range of phase-shifter l for any other numerical relation of frequencies F and F/N can readily be determined.

The phase-shifter may be one of any of the suitable known types including those utilizing electromagnetic or electro-static coupling, a re- `sistance-reactance bridge or electronic phaseshift networks. For simplicity a resistance capacity bridge such as shown in Figures 4 and 5 is preferred. The condensers K, KI are each of ohmic reactance equal, at the impressed operating frequency, to the resistance of resistors R, Ri. When, as in first example above described, a Ou to phase shift is desired, only one of the resistors is Variable Whereas both are adjustable, 1n unison, when 0 to 180 phase shift is desired. These networks have the advantage that the output amplitude remains constant for the different phase settings.

For transmission to a remote point, the output of mixer 3 of Figure l, or of any of the modifications hereinafter described, may be utilized to modulate a radio transmitter or it may be im- At the receiving station, the complex wave isY separated by `filter into its components. The reference. frequency is impressed upon'asuitable phase indicator [i: the other component F/N is first impressed on the frequency-convertor 1 for` conversion to the same frequency as the reference component and then at"reference` frequency upon the phase-meter or indicator BI If for example, in the transmitter as above specifically described, the phase of frequency F/N is shifted 45 by phase-shifter 4, the output:-

of converter 1 is 180 out of phase with respect to the output F of filter 5 and accordingly the movable elementof phase-meter 6 moves to position corresponding with the letter M setting of phase shifter 4,

Another channel for transmission of intelligence may be provided by addition of another source of frequency'. F/M having nxed time relation to frequency F and with respect thereto an integral multiple relation different from that of frequency F/M. By way of illustration, the frequency of source IA may be' one-half the frequency of source2 and twice that of source I in which event the phase-shifter 4a should be of type, Figure 5 forv example, suited to afford a phase-shift'of 0 to 180.

To receive'this intelligence at the same or different receiving station, there isthere provided a filter of known type suited to separate the two or more components of the complex` wave emitted by the transmitter. The reference frequency component and the outputv of the frequency converter 1A, a doubler nthis specific case, are impressed-cna phase-meter such as 5. The outputs of thetwo or morev converters are fed to a common phase-meter of the cathode-ray type and maybe concurrentlyobserved provided the signals from the different channels have some characteristics, other than phase displacement, to distinguish them: by way of example, as later rescribe'd, diiferent rates of interruption may serve todistinguish them.

Because of practical difficulties in maintenance of fixed time relation-between two or more independent sources of frequency, it is desirable that all' frequenciesbederived from a single source. As indicated in Figure, the source `I may be utilized tofcontrol the frequency of a multi-vibrator or'sub-harmonic' generator 8 whose square-wave output, Figure', is smoothed to sine-wave shape by resonantnlter 9 disposed'in advanceo'fphaseshifter Preferably, a buffer stage is interposed between the oscillator comprised in source I andthe multi-vibrator to avoid interaction affecting frequency stability. For multi-channel operation, additional multi-vibrators locking in at different sub-harmonics of the oscillator are used and with each, in advance of its associated phase-shifter, is associated a suitable filter ensuring' sine-'wave form of the corresponding output sub-harmonic frequency.

Another phase-shifter, Figures 8', l2, comprises two slide wires II and I2 eachy tapped at four points displaced 90. The voltage E, impressed on slidewire II at two taps which are 180-electrical degrees apart, risl90" out of phaselwith respect to the voltagey EI impressed on slidewire I2 at two taps which are 180 electrical degrees' apart. The other taps of the slidewires are interconnected as. shown and their movable contacts I3, Ill are" disposed '"and movablein unison with the 'result the phase' 'relation ofA voltages E2 and E3 may be varied throughout the range of 0d to 180. The movable contacts may engage thsucce'ssive turns of the resistors II, I2 to afford a substantially gradual change in phase shift as when itfis" desired to transmit bearing information or each may engage a series of fixed contacts connected'jto points angularly displaced along theassociatd resistor to effect step-bystepphase adjiistment as when it is desired to transmit letters,- numerals, units of distance or height, speeds and the like.

vTo obtain a voltage E which is displaced in phase 90 from'lvoltage EI, there is preferably provided, Figure 8, a phase-splitting network, comprising resistor I5 and associated condenser I6 of much lower ohmic value than resistor I5 at the impressed frequency F and an amplifier I1. The amplifier makes up `for loss of voltage due to the low drop across` condenser I6 and is so designed or adjuste'd-thatvoltages 'E and El are of equal magnitude. An automatic volume control arrangement I8 maintains this equality for change in frequency of voltage E2 should that occur.

In Figures Qand 10 isv shown'av system suited for cathode-rayy tube presentation of the multifrequency complex wave outputv of the type transmitters shown in Figures 1 and 2.

n brief, the reference frequencyv ofl the signal is passed to the phase-splitter ISt'o provide two voltages in phase quadrature which are applied to the horizontal and vertical deflection plates of cathode-ray tube 6A so to effect rotation of the cathode ray spot which is'made visible or intensined under control of the grid 20 whose potential is suddenly changed in response to the other component of the signal wave. In addition,if desired, the spot may be deflected radially by controlling the'potential of the central electrode 2BA concurrently with'that of grid 2e. Thus, as shown in Figure 1l, for each position of the phase-setter of any of transmitters p-reviously described, there is produced a correspondingly angularly positioned spot or radial trace indicative of certain intelligence, such as a bearing, speed, letter or a number.

Inasmuch as the individual elements of the syst-ern of Figure 9 are per se wellfknown and as circuit constants depend upon the tubes and frequencies shown,- the circuit diagram, Figure i0, need not be discussed in` detail.

The phase shifter Pisis'provided to'cornp'ensate for any undesired phase-shift introduced by circuit components of the receiving system or during propagation ofthe signal. Once set t'o effect lcompensation it need usually be adjusted only infrequently if at all; The cathode follower stages 26 and 2l afford coupling of the multi-vibrator 24 t'o the control` electrode 20 and 20A of the cathode-ray tube and the circuit-constants of the radialv pulser =are`chos`en to afford a suitably narrow width, for example 1, of the radialtrace.

On or adjacent the face of indicator tube, Figure 1l, there are three scales or dials one for affording indicatiohof bearingga second for indicating speed and the third for indicating letters or numbers. At the associated transmitter, there is included in the output system of the phaseshifter 4B a keying arrangement for imparting identifying characteristics to signals correspond'- ing with the different types of information. For example, when the switches 28A, 28B operable by a common control knob 28, Figure 13, are in the full line position shown in Figure 12, the slidewire contacts I 3, I4 may be positioned by knob 29 to any angular position in the range 0 to 360 and accordingly at the receiving station or stations a radial trace or spot will appear on the tube 6 at the corresponding angular position. The spot or trace will be steady and the observer will know he is to read the compass or bearing scale.

When contacts 28A, 28B are moved to the next lower fixed contacts, the switches 38A, 30B and the interrupter switch 3| are included in circuit. The fixed contacts engageable by 28A, 28B are connected to taps of the slidewires H, I2 so that for each change position of control knob 30 of contacts 30A, 30B the output of the phase-shifter 4B is shifted in phase to extent corresponding with increase or decrease from one standard speed to another. The output of the phase-shifter is interrupted at suitable perdetermined rate by the motor-drive cam switch 3I or equivalent with the result the trace or spot on the receiver indicator1 blinks rapidly or is broken informing the observer that the speed scale is to be read.

When contacts 28A, 28B are moved tc the next lower position, Figure 12, the banks 32A, 32B of lcontacts and the interrupter switch 33 are connected through cables 34A, 34B to taps from the slide-wires II and I2. Preferably the keys for operating the movable contacts of the banks 32A, 32B are arranged to simulate a typewriter keyboard, Figure 13. As each key is depressed a corresponding pair of movable contacts, one in each bank, complete connections to a pair of taps of slidewires II, I2 to effect a shift in phase corresponding to a particular character. The phaseshifter output is keyed by interrupter switch 33 at rate different, for example lower, from rate of the speed interrupter switch 3| so that the observer at the receiving station correlates the position of the slowly blinking spot or dash-type trace with the ring of characters and so can spell out or translate the various spot positions to message form, in plain or coded language.

Coded messages may be sent from plain text messages .by interposing a connection-changing plug and jack code-board between slide-wires I I, I2 and the banks 32A, 32B of the typewriter keyboard. At the receiving station, the message may be decoded or may be directly read from the indicator 6A if the outer chart is replaced by one corresponding with the particular code-board in use at the transmitter.

Although for purpose of explanation, we have described various modifications of our invention it is not limited thereto but is coextensive in scope with the appended claims.

'Ihe invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A communication system comprising a source of reference frequency, means for deriving from said source a frequency which is a sub-harmonic of said reference frequency, a mixer stage upon which said frequencies are impressed, and a phase-shifter adjustable in accordance with information to be transmitted interposed between said mixer stage and said means.

2. A communication system comprising a source of reference frequency, a multi-vibrator controlled by said source to generate another frequency harmonically related to the reference frequency, a mixer stage upon which said frequencies are impressed, a phase-shifter adjustable in accordance with information to be transmitted interposed between said mixer stage and said multi-vibrator, and a filter in advance of said phase-shifter to suppress frequencies other than said second-named frequency.

3. A communication system comprising: a transmitting station including a reference frequency voltage source of fixed frequency and a source of a fixed frequency voltage bearing an integral multiple relation to said reference frequency source, means for shifting the phase of one of said voltage sources in accordance with information to be communicated and mixing means for combining the output of said voltage sources; a receiving means including means separating the reference frequency voltage from the said voltage bearing an integral relation with respect thereto, means for converting one of said separated voltages to the same frequency as the other of said separated voltages and means responsive to the relative phase relations of the said voltages of the same frequency.

4. A communication system employing. a xed radio frequency reference component and a further frequency component bearing xed harmonic relation thereto and further comprising a lter for separating a complex wave into said reference frequency component and said further frequency component, a phase-meter having one input circuit upon which said reference frequency is impressed, and a second input circuit for said phase-meter including a convertor upon which said further frequency component is impressed for conversion to the reference frequency in advance of said phase-meter.

ADOLPH WILLIAM BORSUM. WILHELM W. BROCKWAY.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,236,374 Marrison Mar. 25, 1941 2,256,487 'Moseley et a1 Sept. 23, 1941 2,363,941 Busignies Nov. 28, 1944 2,402,973 Moore July 2, 1946 

